In general, rubber modified aromatic vinyl resins can have excellent mold processability, high mechanical properties, especially impact strength, and good appearance and have accordingly been widely used in the production of many electric or electronic goods and office equipment, among other products. However, rubber modified aromatic vinyl resins can readily catch on fire when they are used in heat-emitting products, such as computers, facsimile machines and the like or high-voltage products. Therefore, attempts have been made to improve the flame-retardant property of rubber modified aromatic vinyl resins.
A widely known method for imparting flame retardancy to rubber modified aromatic vinyl resins is the addition of halogen-containing compounds. Examples of halogen-containing compounds include, for example, polybromodiphenyl ether, tetrabromobisphenol-A, epoxy compounds substituted by bromine, and the like.
Antimony-containing compounds may be employed with halogen-containing compounds to further increase the flame retardancy of the same. However, methods for improving the flame-retardant properties of resins using a halogen- and antimony-containing compound are disadvantageous because hydrogen halide gases released by halogen-containing compounds during molding processes can corrode the mold. Further, such compounds can emit toxic gases if ignited. Polybromodiphenyl ether, which is widely used as a halogen-containing flame retardant, can produce toxic gases such as dioxin or difuran during combustion, and thus a major concern in this field is to develop a flame retardant that does not include a halogen-containing compound.
U.S. Pat. No. 3,639,506 discloses a resin composition using a monomeric aromatic phosphoric acid ester such as a triphenylphosphate with a blend of a styrenic resin and a polyphenylene ether resin. However, the addition of triphenylphosphate reduces the heat-resistance property of the resin composition. Such blends also can exhibit a so called “juicing crack phenomenon” because the triphenylphosphate has high volatility, and thereby can form deposits on the surface of a molding product during a molding process.
WO 2005/012416 discloses a thermoplastic resin composition comprising a rubber modified styrene comprising resin and a ring-shaped alkyl phosphonic acid compound stated to have good dripping flame retardancy without heat resistance deterioration or a volatility problem.
In order to prevent discoloration by light and to improve weatherability of the resin composition, hindered amine light stabilizers (HALS compounds) or UV absorbers (such as benzotriazol based compounds, bezophenone based compounds, and hydroxyphenyl triazine compounds) have been generally employed. HALS compounds may increase weatherability by inhibiting photodecomposition of the polymer. UV absorb ers may increase weatherability of the resin by absorbing UV light. However, it is necessary to add HALS compounds or UV absorbers in a large amount to obtain sufficient weatherability.